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          浅谈设计模式 - 简单工厂模式（二）
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        <h1 id="浅谈设计模式-简单工厂模式（二）"><a href="#浅谈设计模式-简单工厂模式（二）" class="headerlink" title="浅谈设计模式 - 简单工厂模式（二）"></a>浅谈设计模式 - 简单工厂模式（二）</h1><h2 id="前言："><a href="#前言：" class="headerlink" title="前言："></a>前言：</h2><p>​    对于学习设计模式，我推荐：<strong>《HeadFirst设计模式》</strong>和<strong>《大话设计模式》</strong>。另外设计模式推崇学以致用。看到任何知识之前，先想想我能学到什么，带着问题去看待问题，将会使得学习事半功倍，否则就是事倍功半。</p>
<p>​    不要过分拘泥于设计模式的类和形式，只要记住一点：将<strong>变与不变抽离的过程</strong>就是设计模式</p>
<a id="more"></a>

<h3 id="为什么设计模式学了就忘？"><a href="#为什么设计模式学了就忘？" class="headerlink" title="为什么设计模式学了就忘？"></a>为什么设计模式学了就忘？</h3><ul>
<li>不敢尝试（当然也不要过度自信，看到代码就想用设计模式）</li>
<li>过于关注设计模式的结构，忘记了业务本身。<ul>
<li>很多时候我们拘泥于形式和设计，纠结于用什么设计模式，其实设计模式本身就是继承，封装，多态的三者结合，很多时候只要可以解决问题，就不需要用过多的技巧</li>
</ul>
</li>
<li>学习之前神志不清<ul>
<li>大致就是邯郸学步，看到别人学设计模式，自己也跑去学设计模式</li>
</ul>
</li>
</ul>
<p>很多人学了设计模式之后隔了一段时间之后，发现自己不使用，忘得一干二净（我也是）。所以希望这些设计模式更多的是结合一些比较实际一点的需求（尽量），毕竟设计模式学了就是拿来用的，如果不用不如不要学，去看点动漫电视剧啥的放松一下。</p>
<h2 id="什么是简单工厂模式？"><a href="#什么是简单工厂模式？" class="headerlink" title="什么是简单工厂模式？"></a>什么是简单工厂模式？</h2><h3 id="现实理解："><a href="#现实理解：" class="headerlink" title="现实理解："></a>现实理解：</h3><p>简单工厂从字面意思来看，就如同我们平常的工厂一般，我们想要重复的生产某样物品，就需要建设工厂不断生产。我们需要给工厂下达指令，比如生产一批“苹果”，生成一批“香蕉”。我们只需要只会工厂生产，而不需要去理会内部的细节。</p>
<h3 id="工厂模式："><a href="#工厂模式：" class="headerlink" title="工厂模式："></a>工厂模式：</h3><p>简单工厂模式，是一种<strong>创建型设计模式</strong>，定义简单工厂，负责为具体操作对象生成需要的操作类，把创建对象和使用对象进行分开，使用对象方只需要传入调用简单工厂的工厂方法进行创建对象。</p>
<h2 id="简单工厂的特点："><a href="#简单工厂的特点：" class="headerlink" title="简单工厂的特点："></a>简单工厂的特点：</h2><ol>
<li>返回抽象的接口或者父类，由工厂管理子类创建过程</li>
<li>让创建过程变成一个黑盒</li>
<li>封闭创建过程，客户端只需要关注结果。</li>
</ol>
<h2 id="工厂模式优缺点："><a href="#工厂模式优缺点：" class="headerlink" title="工厂模式优缺点："></a>工厂模式优缺点：</h2><p>优点：</p>
<ol>
<li>使用创建工厂的方法，我们实现了获取具体对象和生产对象的解耦，由生产对象的工厂通过我们传入的参数生产对应的对象，调用方只需要传递需要生产的对象来实现具体的效果。</li>
<li>解耦了创建和被创建的过程。</li>
<li>根据不同的逻辑判断生成不同的具体对象。</li>
</ol>
<p>缺点：</p>
<ol>
<li>每增加一个工厂对象具体的实现类，就需要增加<code>if/else</code>不利于维护</li>
<li>大量的子类会造成工厂类的迅速膨胀和臃肿</li>
<li>简单工厂的方法一般处理简单的业务逻辑，如果创建逻辑复杂不建议使用。</li>
</ol>
<h2 id="实际案例："><a href="#实际案例：" class="headerlink" title="实际案例："></a>实际案例：</h2><p>下面的案例是个人理解，可能存在偏差，不同人理解有差异。欢迎给出建议。</p>
<h3 id="场景模拟："><a href="#场景模拟：" class="headerlink" title="场景模拟："></a>场景模拟：</h3><p>​    我们以经典的任天堂游戏坦克大战为例，在进入游戏的关卡的时候，会出现我方的坦克和敌人的坦克，我方坦克和地方坦克不仅形状不同，而且很脆，但是敌人的坦克根据颜色需要打好几枪才会毁灭，那么如果用代码来模拟是什么样的呢？</p>
<h3 id="不使用设计模式："><a href="#不使用设计模式：" class="headerlink" title="不使用设计模式："></a>不使用设计模式：</h3><p>根据场景，我设计了如下的图表</p>
<p><img src="https://gitee.com/lazyTimes/imageReposity/raw/master/img/20210125224612.png" alt=""></p>
<p>​    按照正常方式，我们的定义了一个坦克的父类，接着我们需要定义三个子类来继承父类坦克，以实现自己的扩展。当我们需要创建坦克的时候，我们需要纠结所有的细节，比如到底是创建我方坦克还是敌人坦克，我方的坦克位置，敌人的坦克位置，我方的血量，敌人的血量，等等，<strong>从创建坦克到销毁坦克的所有过程，都由我们进行参与。</strong></p>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">+ 坦克抽象类 Tank.java</span><br><span class="line">+ 老鼠坦克 MouseTank.java</span><br><span class="line">+ 我方坦克 MyTank.java</span><br><span class="line">+ 巨型坦克 BigTank.java</span><br><span class="line">+ 测试类 Main.java</span><br></pre></td></tr></table></figure>



<p>具体的代码实现如下：</p>
<ul>
<li>坦克的抽象类：</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 坦克的抽象类，定义坦克的行为</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> zxd</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@version</span> 1.0</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@date</span> 2021/1/25 0:14</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">abstract</span> <span class="class"><span class="keyword">class</span> <span class="title">Tank</span> </span>&#123;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 坦克hp</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">protected</span> <span class="keyword">int</span> hp;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 坦克子弹</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">protected</span> List&lt;Object&gt; bullet;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 移动的方法s</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="function"><span class="keyword">abstract</span> <span class="keyword">void</span> <span class="title">move</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 攻击</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="function"><span class="keyword">abstract</span> <span class="keyword">void</span> <span class="title">attack</span><span class="params">()</span></span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 停止</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="function"><span class="keyword">abstract</span> <span class="keyword">void</span> <span class="title">stop</span><span class="params">()</span></span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<ul>
<li>老鼠坦克</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 老鼠坦克</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> zxd</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@version</span> 1.0</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@date</span> 2021/1/25 22:02</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">MouseTank</span> <span class="keyword">extends</span> <span class="title">Tank</span> <span class="keyword">implements</span> <span class="title">Runnable</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">display</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"长得尖尖的，很像老鼠"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">MouseTank</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        <span class="comment">// 坦克假设只有一条命</span></span><br><span class="line">        hp = <span class="number">1</span>;</span><br><span class="line">        <span class="keyword">new</span> Thread(<span class="keyword">this</span>).start();</span><br><span class="line">        bullet = <span class="keyword">new</span> ArrayList&lt;&gt;();</span><br><span class="line">        <span class="comment">// 初始化添加六发子弹</span></span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">move</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"老鼠坦克移动"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">attack</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"老鼠坦克开枪"</span>);</span><br><span class="line">        <span class="comment">// ..弹出子弹</span></span><br><span class="line">        <span class="keyword">if</span> (bullet.size() &lt;= <span class="number">0</span>) &#123;</span><br><span class="line">            System.err.println(<span class="string">"老鼠坦克没有子弹了"</span>);</span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 老鼠坦克一次性开两枪</span></span><br><span class="line">        bullet.remove(bullet.get(bullet.size() - <span class="number">1</span>));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">stop</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"停止"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        <span class="keyword">while</span> (<span class="keyword">true</span>) &#123;</span><br><span class="line">            <span class="comment">// 一旦创建就开始移动</span></span><br><span class="line">            move();</span><br><span class="line">            <span class="comment">// 漫无目的开枪</span></span><br><span class="line">            attack();</span><br><span class="line">            attack();</span><br><span class="line">            <span class="comment">// 做完一轮操作歇一秒</span></span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                Thread.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 随机停止</span></span><br><span class="line">            <span class="keyword">if</span> (<span class="keyword">new</span> Random(<span class="number">100</span>).nextInt() % <span class="number">2</span> == <span class="number">0</span>) &#123;</span><br><span class="line">                stop();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<ul>
<li>巨型坦克</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 巨型坦克</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> zxd</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@version</span> 1.0</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@date</span> 2021/1/25 22:14</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">BigTank</span> <span class="keyword">extends</span> <span class="title">Tank</span> <span class="keyword">implements</span> <span class="title">Runnable</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">display</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"巨型坦克"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">BigTank</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        <span class="comment">// 带颜色的坦克有很多条命</span></span><br><span class="line">        hp = <span class="number">5</span>;</span><br><span class="line">        <span class="keyword">new</span> Thread(<span class="keyword">this</span>).start();</span><br><span class="line">        bullet = <span class="keyword">new</span> ArrayList&lt;&gt;();</span><br><span class="line">        <span class="comment">// 初始化添加三发子弹</span></span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">move</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"巨型坦克移动"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">attack</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"巨型坦克开枪"</span>);</span><br><span class="line">        <span class="comment">// ..弹出子弹</span></span><br><span class="line">        <span class="keyword">if</span> (bullet.size() &lt;= <span class="number">0</span>) &#123;</span><br><span class="line">            System.err.println(<span class="string">"巨型坦克没有子弹了"</span>);</span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 老鼠坦克一次性开两枪</span></span><br><span class="line">        bullet.remove(bullet.get(bullet.size() - <span class="number">1</span>));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">stop</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"巨型坦克停止"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title">run</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        <span class="keyword">while</span> (<span class="keyword">true</span>) &#123;</span><br><span class="line">            <span class="comment">// 一旦创建就开始移动</span></span><br><span class="line">            move();</span><br><span class="line">            <span class="comment">// 漫无目的开枪</span></span><br><span class="line">            attack();</span><br><span class="line">            <span class="comment">// 做完一轮操作歇两秒，</span></span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                Thread.sleep(<span class="number">2000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 随机停止，活动没有老鼠坦克频繁</span></span><br><span class="line">            <span class="keyword">if</span> (<span class="keyword">new</span> Random(<span class="number">1000</span>).nextInt() % <span class="number">2</span> == <span class="number">0</span>) &#123;</span><br><span class="line">                stop();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<ul>
<li>我方坦克</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 我方坦克</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> zxd</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@version</span> 1.0</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@date</span> 2021/1/25 21:58</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">MyTank</span> <span class="keyword">extends</span> <span class="title">Tank</span></span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="title">MyTank</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        <span class="comment">// 我方坦克假设只有一条命</span></span><br><span class="line">        hp = <span class="number">1</span>;</span><br><span class="line">        bullet = <span class="keyword">new</span> ArrayList&lt;&gt;();</span><br><span class="line">        <span class="comment">// 初始化添加三发子弹</span></span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">        bullet.add(<span class="keyword">new</span> Object());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">move</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"移动"</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">attack</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"攻击地方坦克"</span>);</span><br><span class="line">        <span class="comment">// ..弹出子弹</span></span><br><span class="line">        <span class="keyword">if</span>(bullet.size() == <span class="number">0</span>)&#123;</span><br><span class="line">            System.err.println(<span class="string">"没有子弹了"</span>);</span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        bullet.remove(bullet.get(bullet.size() -<span class="number">1</span>));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="function"><span class="keyword">void</span> <span class="title">stop</span><span class="params">()</span> </span>&#123;</span><br><span class="line">        System.err.println(<span class="string">"停止"</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<ul>
<li>测试类：</li>
</ul>
<blockquote>
<p>建议使用单元测试，这里图方便没有用</p>
</blockquote>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 这种频繁的new，让我们逐渐变成面向过程编程。。。。</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> args</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>&#123;</span><br><span class="line">        <span class="comment">// 虽然我们可以自己生产坦克，但是我们每次都需要自己手动去生产对应的坦克。这种频繁的new 操作</span></span><br><span class="line">        Tank bigTank1 = <span class="keyword">new</span> BigTank();</span><br><span class="line">        Tank bigTank2 = <span class="keyword">new</span> BigTank();</span><br><span class="line">        Tank bigTank3 = <span class="keyword">new</span> BigTank();</span><br><span class="line">        Tank bigTank4 = <span class="keyword">new</span> BigTank();</span><br><span class="line">        <span class="comment">// 有多少个对象，就有多少个new</span></span><br><span class="line">        Tank mouseTank1 = <span class="keyword">new</span> MouseTank();</span><br><span class="line">        Tank mouseTank2 = <span class="keyword">new</span> MouseTank();</span><br><span class="line">        Tank mouseTank3 = <span class="keyword">new</span> MouseTank();</span><br><span class="line">        Tank mouseTank4 = <span class="keyword">new</span> MouseTank();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 我方坦克，需要自己操作</span></span><br><span class="line">        Tank myTank1 = <span class="keyword">new</span> MyTank();</span><br><span class="line">        Tank myTank2 = <span class="keyword">new</span> MyTank();</span><br><span class="line"></span><br><span class="line">    &#125;<span class="comment">/*//运行结果：</span></span><br><span class="line"><span class="comment">        停止</span></span><br><span class="line"><span class="comment">        老鼠坦克移动</span></span><br><span class="line"><span class="comment">        老鼠坦克开枪</span></span><br><span class="line"><span class="comment">        老鼠坦克开枪</span></span><br><span class="line"><span class="comment">        停止</span></span><br><span class="line"><span class="comment">        老鼠坦克移动</span></span><br><span class="line"><span class="comment">        老鼠坦克开枪</span></span><br><span class="line"><span class="comment">        巨型坦克移动</span></span><br><span class="line"><span class="comment">        巨型坦克开枪</span></span><br><span class="line"><span class="comment">        老鼠坦克开枪</span></span><br><span class="line"><span class="comment">        老鼠坦克没有子弹了</span></span><br><span class="line"><span class="comment">        停止</span></span><br><span class="line"><span class="comment">        老鼠坦克移动</span></span><br><span class="line"><span class="comment">        老鼠坦克开枪</span></span><br><span class="line"><span class="comment">        老鼠坦克没有子弹了</span></span><br><span class="line"><span class="comment">        老鼠坦克开枪</span></span><br><span class="line"><span class="comment">        老鼠坦克没有子弹了</span></span><br><span class="line"><span class="comment">        巨型坦克移动</span></span><br><span class="line"><span class="comment">        巨型坦克开枪</span></span><br><span class="line"><span class="comment">    */</span></span><br></pre></td></tr></table></figure>

<h4 id="上面的代码有什么问题："><a href="#上面的代码有什么问题：" class="headerlink" title="上面的代码有什么问题："></a>上面的代码有什么问题：</h4><p>咋看一下好像没啥问题呀，我们既有定义抽象的父类，同时又定义了子类去继承，在需要的时候我们直接new就是了。</p>
<p>其实问题就出在new这一步，可以说我们<strong>写烂代码的第一步就是new</strong>。因为我们掉进了“细节”的陷阱，下面我们分析一下我们的代码有什么问题：</p>
<ol>
<li>我要加一个坦克，虽然可以继承，但是如果要加入到战场，需要我们记住新坦克，并且new出来</li>
<li>我想要老鼠坦克，却不小心new了一个普通地方坦克，当代码较少的时候可能没啥问题，但是如果代码多了，我们要花大量时间查找</li>
<li>我们的测试类掌控了一切，他的活太重了，不仅需要new，还需要new之后的所有操作。</li>
</ol>
<h3 id="用简单工厂模式改进："><a href="#用简单工厂模式改进：" class="headerlink" title="用简单工厂模式改进："></a>用简单工厂模式改进：</h3><p>既然知道了有什么问题，那么我们可以加入一个简单工厂类来管理坦克的创建过程</p>
<p><img src="https://gitee.com/lazyTimes/imageReposity/raw/master/img/20210126000032.png" alt=""></p>
<p>增加工厂类 <code>TankFactory.java</code></p>
<p>用工厂来管理具体的坦克创建过程:</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 坦克工厂，专门负责生产坦克</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> zxd</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@version</span> 1.0</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@date</span> 2021/1/25 22:27</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">TankFactory</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 创建坦克</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@return</span></span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> Tank <span class="title">createTank</span><span class="params">(String check)</span></span>&#123;</span><br><span class="line">        Tank tank = <span class="keyword">null</span>;</span><br><span class="line">        <span class="keyword">if</span>(Objects.equals(check, <span class="string">"my"</span>))&#123;</span><br><span class="line">            tank = <span class="keyword">new</span> MyTank();</span><br><span class="line">        &#125;<span class="keyword">else</span> <span class="keyword">if</span>(Objects.equals(check, <span class="string">"mouse"</span>))&#123;</span><br><span class="line">            tank = <span class="keyword">new</span> MouseTank();</span><br><span class="line">        &#125;<span class="keyword">else</span> <span class="keyword">if</span> (Objects.equals(check, <span class="string">"big"</span>))&#123;</span><br><span class="line">            tank = <span class="keyword">new</span> BigTank();</span><br><span class="line">        &#125;<span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> UnsupportedOperationException(<span class="string">"当前坦克不支持生产"</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> tank;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<p>我们重写单元测试：</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * 单元测试</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@author</span> zxd</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@version</span> 1.0</span></span><br><span class="line"><span class="comment"> * <span class="doctag">@date</span> 2021/1/25 22:15</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">Main</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * 我们将生产坦克的过程全部交给了工厂来处理</span></span><br><span class="line"><span class="comment">     * 可能还是奇怪，这和刚才没有什么区别呀？</span></span><br><span class="line"><span class="comment">     * 我们来看下区别：</span></span><br><span class="line"><span class="comment">     * 1. 创建的过程没有了，虽然是一个简单的new，但是new的过程交给了工厂</span></span><br><span class="line"><span class="comment">     * 2. 我们后续如果要在坦克加入别的东西，只需要去改工厂类和具体的实现类，不需要该此处代码</span></span><br><span class="line"><span class="comment">     * 3. 如果不支持的操作，工厂还可以通知我们这样做不对</span></span><br><span class="line"><span class="comment">     * <span class="doctag">@param</span> args</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">main</span><span class="params">(String[] args)</span> </span>&#123;</span><br><span class="line"></span><br><span class="line">        TankFactory tankFactory = <span class="keyword">new</span> TankFactory();</span><br><span class="line"></span><br><span class="line">        Tank my = tankFactory.createTank(<span class="string">"my"</span>);</span><br><span class="line">        Tank mouse = tankFactory.createTank(<span class="string">"mouse"</span>);</span><br><span class="line">        Tank big = tankFactory.createTank(<span class="string">"big"</span>);</span><br><span class="line">        <span class="comment">// 我要一个没有的设计过的坦克</span></span><br><span class="line">        Tank mybig = tankFactory.createTank(<span class="string">"mybig"</span>);</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    &#125;<span class="comment">/*//</span></span><br><span class="line"><span class="comment">    运行结果：</span></span><br><span class="line"><span class="comment">    Exception in thread "main" 老鼠坦克移动</span></span><br><span class="line"><span class="comment">    巨型坦克移动</span></span><br><span class="line"><span class="comment">    老鼠坦克开枪</span></span><br><span class="line"><span class="comment">    巨型坦克开枪</span></span><br><span class="line"><span class="comment">    老鼠坦克开枪</span></span><br><span class="line"><span class="comment">    java.lang.UnsupportedOperationException: 当前坦克不支持生产</span></span><br><span class="line"><span class="comment">	at com.headfirst.factory.use.TankFactory.createTank(TankFactory.java:27)</span></span><br><span class="line"><span class="comment">	at com.headfirst.factory.use.Main.main(Main.java:33)</span></span><br><span class="line"><span class="comment">    */</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h4 id="改进之后有什么变化："><a href="#改进之后有什么变化：" class="headerlink" title="改进之后有什么变化："></a>改进之后有什么变化：</h4><ol>
<li>首先，我们把创建的具体过程交给了工厂，不在需要关注创建的细节</li>
<li>如果需要修改创建的过程，不需要改客户端代码，只需要修改工厂的代码</li>
<li>扩展同样只需要继承工厂的生产抽象对象即可。</li>
</ol>
<h2 id="简单工厂模式在spring中的体现："><a href="#简单工厂模式在spring中的体现：" class="headerlink" title="简单工厂模式在spring中的体现："></a>简单工厂模式在spring中的体现：</h2><p><code>@Bean</code>注解让我们可以在被Spring管理的对象定义Bean的创建过程，而此时这个类就类似一个工厂，对象的创建细节被封装在具体的方法之中，同时这种方式也是一种<code>单例设计模式</code>，我们定义的<code>@Bean</code>是单例的，在需要的地方可以使用<code>Spring</code>的注解进行注入而不需要自己new对象。</p>
<h2 id="总结："><a href="#总结：" class="headerlink" title="总结："></a>总结：</h2><p>案例可能不是十分贴切，因为仅仅只有一个new方法是不需要用工厂模式的，但是这里是个人思考之后觉得最能够联想到的情况，就使用了坦克这个例子作为文章的主体。</p>
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